Amplify-and-forward (AF) relaying protocols are an important class of cooperative relaying protocols. Non-orthogonal AF (NAF) relaying, where the source sends new information while the relay forwards previously transmitted information, can achieve higher transmission rates than orthogonal relaying, where the source and relay do not transmit simultaneously. However, all the transmitted symbols in NAF relaying do not achieve full cooperative diversity. Precoding of symbols can address this problem. Recently, a coordinate interleaved NAF (CINAF) protocol has been proposed for NAF relaying with a single-antenna relay.

In this paper, we extend this protocol to the multi-antenna relay (or multiple cooperative relays) setting. The linear transformation F used for amplifying at the relay is identified as an important component. Four designs for F are presented and compared extensively using simulations. The importance of channel state information (CSI) at the relay is studied. While full CSI about the source-relay channel is used, limited CSI about the relay-destination channel combined with antenna selection at the relay is observed to be sufficient to achieve most of the performance gain.

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